Printing of moving yarns

ABSTRACT

The invention concerns a method of and an apparatus for applying dyestuffs to yarns at spaced intervals therealong whereby opposed cooperating members act on the yarn simultaneously from opposite sides thereof, the members each being moved towards the yarn so as to make contact therewith. The invention is of particular use in the selective application of a range of dyestuffs to a moving yarn at intervals therealong and according to a predetermined pattern, a plurality of groups of cooperating members being arranged in succession in the direction of yarn movement and the individual groups being separately actuable as required to give the said pattern.

United States Patent 1 1 3,600,730

[72] lnventor Raymond Victor Evans [56] References Cited Blackburn W UNITED STATES PATENTS 5 Q A' gig 3 1,311,131 7/1919 Longthome 8/149 t d A 197] 3,227,077 l/l966 Farreretal. 101/172 E 252 zz' I I 3,304,862 2/1967 Lawrenceetal. 101/172 Blackburn, England Primary Examiner-William I. Price [32] Priority 013.22,!968 Att0rneysMarshall J. Breen, Chester A. Williams and Julian 331 Great Britain Falk 11 50061168 ABSTRACT: The invention concerns a method of and an apparatus for applying dyestuffs to yarns at spaced intervals therealong whereby opposed cooperating members act on the yarn simultaneously from opposite sides thereof, the members each being moved towards the yarn so as to make contact therewith. The invention is of particular use in the selective [54] PRINTING OF MOVING YARNS 24 Clams 4 Drama: application of a range of dyestufi's to a moving yarn at inter- [52] US. Cl 8/149, vals therealong and according to a predetermined pattern, a 68/203 plurality of groups of cooperating members being arranged in [51] lnt.Cl B05c l/08 succession in the direction of yarn movement and the in- [50] Field of Search [OI/172; dividual groups being separately actuable as required to give 1 18/234, 248, 249; 68/200, 202, 203; 8/ 149, 14 the said pattern.

Patented Aug. 24, 1971 2 Sheets- Sheet 1 INVENTOR: Raymond V. Evans ATTORNEY Patented Aug. 24, 1911 3,600,730

2 Sheets-Sheet 2 INVENTOR: Raymond V Evans ATTORNEY PRINTING OF MOVING YARNS The invention concerns a method of and a means for printing moving yarns and has particular reference to a method of and an arrangement adapted selectively to apply dyestuff to a moving yarn at intervals therealong.

According to the invention a method of applying dyestuff to a yarn at intervals therealong includes the steps of causing cooperating members arranged in spaced adjacent disposition to move thereby temporarily to engage a yarn passing therebetween thereat, one at least of the members carrying dyestuff for application to the yarn.

According to a further feature of the invention a method of selectively applying a plurality. of difi'erent dyestuffs to a yarn at spaced intervals therealong according to a predetermined pattern includes the steps of providing a plurality of groups of cooperating members in successive disposition, each group being associated with a particular color to be applied, the cooperating members of each group being arranged in spaced disposition to allow free passage of a yarn therebetween and together being movable into contact with the yarn, and causing cooperating members of that group corresponding to the selected color to be applied temporarily to move together to engage a yarn passing therebetween, one at least of the said cooperating members carrying dyestuff for application to the yarn.

The invention also includes a dyestuff applicator comprising cooperating members arranged in adjacent spaced disposition, and a displacement means adapted to cause each such member to move towards the other thus'to move into surface which the piston rod 21 of solenoid controlled pneumatic piston and cylinder assembly 22 defining the actuator means 16 aforesaid is secured.

The support means for roller 12, which roller is the pressure roller and consists of a'flanged bobbin having a sleeve of a high density polyurethane foam or other highly absorbent material applied thereto, likewise comprises a bellcrank lever, such lever 23 being pivotally mounted upon a pin 24 secured to a lug 25 formed integrally with the said lever 17 intermediate its pivot axis and that end of the lever which receives the bush 20. The roller 12 is freely rotatably mounted on a stub shaft 26 secured to the bellcrank lever 23 at one end thereof, whilst the opposite end of such lever 23 is loosely couengagement therewith, at least one of the said cooperating members being adapted to apply dyestuff to a yarn passing between the cooperating members. 7 I

Preferably the cooperatingmembers will be two in number.

In a preferred arrangement a plurality of groups of cooperating members is arranged in tandem onebehind the other, each being independently operable on a yarn or yarns passing between the cooperating members of each group thereof by a respective displacement means.

Generally the cooperating means will comprise rollers, each said roller being rotatably, mounted on a pivoted arm, and the displacement will be effected by fluid pressure means.

The invention will now be described further,'by way of example only, with reference to the accompanying drawings'in whichi FIG. 1 is a diagrammatic side elevation ofa dyestufi applicator and illustrates the principles of the construction and operation thereof;

FIG. 2,is a perspective view of a printing module incorporating a plurality of applicators of the character of that shown in FIG. 1 the module being broken away in part and having certain parts omitted in the interests of clarity; and

FIGS. 3 and 4 are diagrammatic front and side elevations respectively of an alternative means for maintaining yarn tension.

The dyestufi applicator is shown diagrammatically in FIG. I and will be seen to comprise two rollers 11, 12 between which a yarn 13 under treatment passes, a support means 14, 15 for each roller whereby each such roller is mounted for pivotal motion about a respective pivot axis, and an actuator means 16 adapted to pivot each said roller to or from an operative position whereat the rollers are in mutual contact one with the other.

The support means 14 for roller 11, which roller is the applicator roller and consists preferably of a rigid cylindrical core having a coating or sleeve of a medium to soft rubber of a shore hardness of 60 applied thereto, comprises a bellcrank lever 17 mounted for pivotal motion about a fixed spindle 18, the roller 11 being freely rotatably mounted upon a stub shaft 19 secured to one end of such lever. A drive means, not shown, is provided for the roller 11. The opposite end of the bellcrank lever 17 is adapted loosely to receive a bush 20 to pled to a fixed pin 27 by a coupling bush 28, the coupling bush being movable longitudinally of the bellcrank throughout a limited extent thus to accommodate the movement of the pivot axis of the lever 23 consequent upon pivotal motion of bellcrank lever 17. I

A dye trough 29 is provided into whicli'the applicator roller 11 extends, such roller 11 moving outwardly of such trough upon pivotal motion thereof towards an operative position. A means is provided for ensuring the maintaining of a constant level of dyestuff in the trough.

In usage, yarn 13 is passed continuously between the rollers ll, 12, such rollers being arranged in spaced disposition one above the other, and the actuator means 16 is energized to pivot the bellcrank lever 17, and in consequence the bellcrank lever 23, to bring the rollers 1 1, 12 together thus to apply dyestuff to the yarn, the frequency of energization and the period of such energization being determined by coloring requirements. The various elements are so dimensioned and the'yarn 13 so positioned relative to the roller when in their rest positionsthat such rollers, when pivoted, move into contact with the yarn without any substantial transverse displacement of the latter by either roller.

By providing an absorbent material atthe surface of roller 12 for use in conjunction with the medium to soft rubber surface to the roller 11, we accurately control the extent of dyestuff application since the compression of roller 12 is limited by the engagement of the shoulders of the bobbins of roller 12 with the surface of roller 11, expressed dy'estuff being absorbed by the upper roller. In this way a precise termination of applied color is much facilitated.

By means of a plurality of applicators spaced at intervals longitudinally of the yarn and by synchronizing the operation of such'applicators, a corresponding number of dyestuffs can be applied'to the yarn at intervals therealong accordingto a required sequence.

Itis to be appreciated that a number of individual yarns may be guided to each applicator for simultaneous treatment thereat, if desired, and that a plurality of applicators can be provided in adjacent side-by-side disposition to deal in a like or a different manner with a multiplicity of yarns.

A practical embodiment of the invention is illustrated in FIG. 2 of the accompanying drawings, such figure showing, in

detail, a typical dyeing module for use in the selective application to each of a multiplicity of yarns and at spaced intervals therealong of a plurality of individual colors.

Referring now to FIG. 2 of the drawings the printing module comprises a plurality of spindles 30, say eight, rotatably mounted in spaced parallel disposition, each such spindle 30 supporting a plurality of applicators, say eight, of the character of that shown in FIG. I, the rotatable spindle 30 of the practical embodiment shown in FIG. 2 corresponding to the spindle 18 of the arrangement shown in FIG. 1. Like reference numerals are used in FIGS. 1 and 2 for the same or similar parts.

The applicator rolls 11 of the module shown in FIG. 2 are driven from the spindle 30 upon which such rolls are mounted, such spindle having drive gears 31 at intervals therealong which mesh with respective cooperating gears 32 secured to and arranged coaxially with the applicator rolls. The applicator rolls 11 are paired longitudinally of the spindle 30 and the gears of each roll of a pair are arranged in closely adjacent disposition between such rolls and mesh with a common drive gear 31.

Spindle 30 is itself driven at one end thereof, all of the spindles 30 being driven from a common shaft extending in the longitudinal direction of the module and hence all being adjustable as regards speed similarly and simultaneously on a single adjustment of the input shaft speed. In practice the spindles 30 will be driven at such a speed as to give a speed differential between the surface speed of the rollers and the rate of advance of the yarns.

A dyetrough 29 is provided in respect of each spindle 30 and itsassociated rollers 11, the troughs 29 being supported upon a vertically adjustable platform 33. The piston and cylinder assemblies 22 (only one of which is shown) and the control means 34 therefor are supported at a position above the respective applicator, and the coupling of the piston and cylinder assembly 22 to the related bellcrank levers 17, 23 is as before.

To facilitate the assembly of the module and the replacement of a spindle 30 and its associated parts should this prove necessary, the spindle is releasably mounted at each end thereof.

At one end, namely its driven end, the spindle engages a block 36 mounted for vertical movement in fixed guide rails 37, the block having a support rod 38 extending downwardly therefrom which is slidably engaged with a trough hole 39 in a retaining bar 41, a cam lever being pivotally mounted in said bar 41 adjacent the hole 39 and being frictionally engageable with such rod 38 thus to hold same against movement. Disengagement of the cam face of the lever 42 from the rod 38 consequent upon pivotal motion of such lever will allow of the vertical displacement of the block 36 and thus of one end of the spindle.

At its other end the spindle engages a plug 43 extending inwardly from an apertured bar 44, the plug 43 being movable in its respective aperture to or from a position whereat it receives the spindle. Retraction of the plug releases the end of the spindle and allows such spindle to be dropped for withdrawal.

The apertured bar 44 by which the spindles are supported at one end and the fixed guide rails 37 upon which the mounting blocks slide at the other are carried on a rigid framework, such framework also carrying the support 46 for the piston and cylinder arrangements 22 and their associated control means 34, and feed conduits 47 for pressure air for the said piston and cylinder arrangement.

The supports 46 for the arrangements 22 comprise four spaced parallel rigid elements extending between respective pairs of upstanding bars 48 secured to elements 49, 51 of the framework, each such arrangement 22 being mounted on the rigid element by a bracket 52 seated thereon. Conveniently, the piston and cylinder arrangements and their related control means are assembled in pairs upon a common bracket in the manner shown in FIG. 2, the bracket being seated on the said rigid element and being positively located thereon by cooperating peg and aperture arrangements (not shown) on the two parts and the piston and cylinder arrangements de- .pending from the bracket and lying one at each side of the element. The rigid elements which define the support 46 are hollow and comprise a channel member having a closure plate secured thereto longitudinally thereof. The lead-in wires for the solenoids defining the control means 34 for the arrangements 22 are located within the said elements. Thefeed conduits 47 for the pressure air for the arrangements 22 are also four in number, such conduits likewise extending between corresponding upstanding bars 48 and each serving the piston and cylinder arrangement of two adjacent applicators. Pressure air is distributed from the conduits 47 to the individual arrangements 22 through flexible tubes 53 extending therebetween. I

By having all of the piston and cylinder arrangements supplied with air through common feed lines we are able, by

. means of a single adjustment, to vary the nip pressure of all of the applicators.

The lead-in wires for the solenoids pass to the rigid elements defining the supports 46 through element 49 of the framework whilst the feed of pressure air to the conduits is by way of an inlet pipe housed within element 51 of such framework.

A yarn tension assemblyzmay be provided at the input end of the module, such assemblyincluding two vertically movable blades 54 arranged in spaced side-by-side disposition and extending transversely of. the path of the yarn through the module. The blades 54 are'actuable independently under the control of respective pneumatic pistonand cylinder units 55, subject only to an interlock which ensures that one blade at least is down at all times, such blades being slidably mounted in a rigid body part 56, extending outwardly through slots 57 therein, and being movable towards or away from a fixed base plate 58 by the units 55. The provision of two blades on the tensioning assembly permits of the threading up of individual yarns whilst maintaining the remaining yarns under tension and moving in the feed direction thereof, the individual blades being lifted in succession to allow entering of the yarn.

As an alternative to the yarn tension assembly shown in FIG. 2 it may be found preferable, particularly if a wide sheet of yarns is involved, to substitute a back tension means for the assembly illustrated, the back tension means serving to hold the yarn under tension even on machine stoppage. The alternative arrangement is shown diagrammatically in FIGS. 3 and 4 and will be seen to comprise two spaced, parallel rollers 60, 61 rotatably mounted in the machine framework 62, the rollers each having a gear 63 on the stub shaft 64 thereof, the two gears 63 being in mesh one with the other. The lowermost roller carries an electromagnetic clutch coupling 65 at the remote end thereof, such coupling being of known form, and being adapted to provide a torque in a direction opposite to that in which the yarn 13 moves thus to takeup slack and to maintain tension. Thus, in the event of a machine stoppage, sagging of the yarn due, for example to moisture takeup, is prevented in that the rollers are rotated in a reverse sense to takeup slack.

Yarn guides (not shown), for example of the kind disclosed in our copending application No. 790,034, filed Jan. 9, 1969, are provided at each end. of the module so as to facilitate the alignment of the yarns with those applicators through which they are to pass.

In addition some four cover members 66 are provided, each such member extending throughout the full length of the framework and being arranged to be supported by such framework, each cover member constituting a guard for corresponding adjacent applicators on each spindle and there being a narrow gap between successive such covers to provide access tothe space between the rolls' of the applicators for threading purposes.

The operation of the module in applying dyestuff to yarns will be self-evident in the light of the description hereinbefore contained of the use of the arrangement shown in FIG. 1, it being understood that the piston and cylinder arrangement 22 will be actuated according to the energizing or otherwise of the respective control means 34 which controls the feed of pressure air to the arrangement 22 according to pattern requirements.

We have found that with the arrangement hereinbefore described and as illustrated in the accompanying drawings we are able to apply a range of dyestuffs to a multiplicity of yarns according to specific predetermined pattern requirements with a high degree of accuracy, the arrangement being such thatthe period of application and the frequency thereof can be varied at will. By having the rollers move to the yarn and apply dyestuff thereto without any substantial transverse displacement thereof it is possible to provide an infinite number of applicators in tandem and to actuate some or all of such applicators at will and without heed to the condition of any other applicator or applicators.

The spindles are readily releasable from their support means, so'each spindle can be removed as a unit in the event of damage or failure or for cleaning purposes, and a new spindle assemblyintroduced in its stead.

A further and important advantage which results from the arrangement described and illustrated concerns the facility with which the yarns can be introduced, there being no obstruction within the limits of the printing module through which the yarns require to be threaded, such yarns following an unimpeded straight line path through the module.

The invention is not limited to the exact feature of the embodiment hereinbefore described since alternatives will readily present themselves to one skilled in the art. Thus, for example, whilst we prefer that the individual rollers are mounted on levers and are moved together on pivotal motion thereof, it may in some circumstances be found preferable to utilize a straight line movement of the cooperating members. Furthermore, whilst solenoid controlled pneumatic piston and cylinder means have been found to be of ready application in the context of the invention, the invention is not limited to the use thereof since direct solenoid actuation may be found convenient in some instances. Indeed, a mechanical linkage may be utilized if desired.

It may be found convenient to provide the cooperating members in the form of shoes or pads rather than as rollers as before described. The surface materials of the cooperating members, and more particularly of the rollers if such are used, will be selected having due regard to the nature of the yarn under treatment and of the physical characteristics of the dyestuff.

Whilst we have shown the succeeding rollers to lie at a common level, advantage may stem from arranging successive rollers at such levels and mounting the rollers in such manner (for example, by adjusting the position of the piston and cylinder arrangement longitudinally of its support relative to the pivot axis of the lever supporting the lower roller), that the points of contact of the rollers, when considered as a whole, with the yarn lie on a curve which matches the natural line taken by the yarn between its points of support.

What I claim is:

1. A method of applying dyestuff to a yarn at intervals therealong including the steps of causing cooperating members arranged in spaced adjacent disposition to move thereby temporarily to engage a yarn passing therebetween thereat, one at least of the members carrying dyestuff for application to the yarn.

2. A method of selectively applying a plurality of different dyestuffs to a yarn at spaced intervals therealong according to a predetermined pattern including the steps of providing a plurality of groups of cooperating members in successive disposition, each group being associated with a particular color to be applied, the cooperating members of each group being arranged in spaced disposition to allow free passage of a yarn therebetween and together being movable into contact with the yarn, and causing cooperating members of that group corresponding to the selected color to be applied temporarily to move together to engage a yarn passing therebetween, one at least of the said cooperating members carrying dyestuff for application to the yarn.

3. A dyestuff applicator comprising cooperating members arranged in adjacent spaced disposition, and a displacement means adapted to cause each such member to move towards the other thus to move into surface engagement therewith, at least one of the said cooperating members being adapted to apply dyestuff to a yarn passing between the cooperating members.

4. A dyestuff applicator as claimed in claim 3 wherein the cooperating members are two in number.

5. A dyestuff applicator as claimed in claim 3 including a plurality of groups of cooperating members arranged in tandem one behind the other, each being independently operable on a yarn or yarns passing between the cooperating members of each group thereof by a respective displacement means.

6. A dyestuff applicator as claimed in claim 5 wherein the cooperating members each comprise a roller.

7. A dyestuff applicator as claimed in claim 6 wherein a first cooperating member comprises an applicator roller arranged to receive a dyestuff, and a second cooperating member comprises a pressure roller engageable with the first such member, the pressure roller comprising a bobbin rotatably mounted on an axle and having a highly absorbent sleeve applied thereto, the sleeve being of an outside diameter in excess of the outside diameter of the flanges of the bobbin.

8. A dyestuff applicator as claimed in claim 7 wherein the applicator roller has a sleeve or coating applied thereto of a medium to soft rubber having a shore hardness of approximately 60.

9. A dyestuff applicator as claimed in claim 3 wherein the cooperating members are displaced by fluid pressure means.

10. A dyestuff applicator as claimed in claim 3 wherein each cooperating member is mounted on a pivotal arm.

11. A dyestuff applicator as claimed in claim 10 including a first pivotally mounted arm upon which a first cooperating member of a group thereof is carried, a second aim to which the first said arm is pivotally secured and which is itself pivotally mounted, a second cooperating member being supported on the said second arm, the first and second cooperating members being movable towards each other into contact with a yarn passing therebetween.

12. A dyestuff applicator as claimed in claim 3 comprising a plurality of groups of cooperating members arranged in adjacent side-by-side disposition and a common shaft upon which the said plurality of groups is supported.

13. A dyestuff applicator as claimed in claim 12 including a machine framework in which the shaft is releasably mounted, fixed guide rails secured to the framework, a block slidably engaged with the fixed guide rails and a locking means adapted to hold the lock in a required position relative to the guide rails, one end of said shaft being supported in the said block.

14. A dyestuff applicator as claimed in claim 13 including a pivotal cam lever and a support rod which carries the said block and with which the cam lever is cooperable.

15. A dyestuff applicator as claimed in claim 14 including an apertured element which forms a part of the framework, and a displaceable plug movable in such element and with which the opposite end of the shaft is cooperable, the plug being captively engaged with the said apertured element.

16. A dyestuff applicator as claimed in claim 3 wherein each displacement means comprises a pneumatic piston and cylinder arrangement.

17. A dyestuff applicator as claimed in claim 16 wherein each piston and cylinder arrangement is an electromagnetically operated such arrangement.

18. A dyestuff applicator as claimed in claim 16 wherein the displacement means is supported on a framework extending above the cooperating members.

19. A dyestuff applicator as claimed in claim 17 wherein said framework includes hollow elements defining a feed conduit for pressure air for the pneumatic piston and cylinder means.

20. A dyestuff applicator as claimed in claim 18 further including a cover mounted on the framework and extending over the displacement means.

21. A dyestuff applicator as claimed in claim 3 further including a yarn tensioningmeans at the input side of the applicator.

22. A dyestuff applicator as claimed in claim 21 wherein the tensioning means includes spaced parallel rollers about which the yarn is passed, the rollers being coupled together for simultaneous rotation and at least one such roller being provided with an electromagnetic coupling adapted to apply a torque in a direction opposite to that of yarn movement.

23. A dyestuff applicator as claimed in claim 3 including a respective dye trough into which that cooperating member of each group thereof adapted to apply a dyestuff extends.

24. A dyestuff applicator as claimed in claim 23 wherein each dye trough is supported upon a vertically adjustable platform. 

2. A methoD of selectively applying a plurality of different dyestuffs to a yarn at spaced intervals therealong according to a predetermined pattern including the steps of providing a plurality of groups of cooperating members in successive disposition, each group being associated with a particular color to be applied, the cooperating members of each group being arranged in spaced disposition to allow free passage of a yarn therebetween and together being movable into contact with the yarn, and causing cooperating members of that group corresponding to the selected color to be applied temporarily to move together to engage a yarn passing therebetween, one at least of the said cooperating members carrying dyestuff for application to the yarn.
 3. A dyestuff applicator comprising cooperating members arranged in adjacent spaced disposition, and a displacement means adapted to cause each such member to move towards the other thus to move into surface engagement therewith, at least one of the said cooperating members being adapted to apply dyestuff to a yarn passing between the cooperating members.
 4. A dyestuff applicator as claimed in claim 3 wherein the cooperating members are two in number.
 5. A dyestuff applicator as claimed in claim 3 including a plurality of groups of cooperating members arranged in tandem one behind the other, each being independently operable on a yarn or yarns passing between the cooperating members of each group thereof by a respective displacement means.
 6. A dyestuff applicator as claimed in claim 5 wherein the cooperating members each comprise a roller.
 7. a dyestuff applicator as claimed in claim 6 wherein a first cooperating member comprises an applicator roller arranged to receive a dyestuff, and a second cooperating member comprises a pressure roller engageable with the first such member, the pressure roller comprising a bobbin rotatably mounted on an axle and having a highly absorbent sleeve applied thereto, the sleeve being of an outside diameter in excess of the outside diameter of the flanges of the bobbin.
 8. A dyestuff applicator as claimed in claim 7 wherein the applicator roller has a sleeve or coating applied thereto of a medium to soft rubber having a shore hardness of approximately 60*.
 9. A dyestuff applicator as claimed in claim 3 wherein the cooperating members are displaced by fluid pressure means.
 10. A dyestuff applicator as claimed in claim 3 wherein each cooperating member is mounted on a pivotal arm.
 11. A dyestuff applicator as claimed in claim 10 including a first pivotally mounted arm upon which a first cooperating member of a group thereof is carried, a second arm to which the first said arm is pivotally secured and which is itself pivotally mounted, a second cooperating member being supported on the said second arm, the first and second cooperating members being movable towards each other into contact with a yarn passing therebetween.
 12. A dyestuff applicator as claimed in claim 3 comprising a plurality of groups of cooperating members arranged in adjacent side-by-side disposition and a common shaft upon which the said plurality of groups is supported.
 13. A dyestuff applicator as claimed in claim 12 including a machine framework in which the shaft is releasably mounted, fixed guide rails secured to the framework, a block slidably engaged with the fixed guide rails and a locking means adapted to hold the lock in a required position relative to the guide rails, one end of said shaft being supported in the said block.
 14. A dyestuff applicator as claimed in claim 13 including a pivotal cam lever and a support rod which carries the said block and with which the cam lever is cooperable.
 15. A dyestuff applicator as claimed in claim 14 including an apertured element which forms a part of the framework, and a displaceable plug movable in such element and with which the opposite end of the shaft is cooperable, the plug being captively engaged with the said apertured element.
 16. A dyestUff applicator as claimed in claim 3 wherein each displacement means comprises a pneumatic piston and cylinder arrangement.
 17. A dyestuff applicator as claimed in claim 16 wherein each piston and cylinder arrangement is an electromagnetically operated such arrangement.
 18. A dyestuff applicator as claimed in claim 16 wherein the displacement means is supported on a framework extending above the cooperating members.
 19. A dyestuff applicator as claimed in claim 17 wherein said framework includes hollow elements defining a feed conduit for pressure air for the pneumatic piston and cylinder means.
 20. A dyestuff applicator as claimed in claim 18 further including a cover mounted on the framework and extending over the displacement means.
 21. A dyestuff applicator as claimed in claim 3 further including a yarn tensioning means at the input side of the applicator.
 22. A dyestuff applicator as claimed in claim 21 wherein the tensioning means includes spaced parallel rollers about which the yarn is passed, the rollers being coupled together for simultaneous rotation and at least one such roller being provided with an electromagnetic coupling adapted to apply a torque in a direction opposite to that of yarn movement.
 23. A dyestuff applicator as claimed in claim 3 including a respective dye trough into which that cooperating member of each group thereof adapted to apply a dyestuff extends.
 24. A dyestuff applicator as claimed in claim 23 wherein each dye trough is supported upon a vertically adjustable platform. 